Cellacefate

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Cellacefate is a reaction product of phthalic anhydride and a partial acetate ester of cellulose. It contains NLT 21.5% and NMT 26.0% of acetyl (C₂H₃O) groups and NLT 30.0% and NMT 36.0% of phthalyl (o-carboxybenzoyl) (C₈H₅O₃) groups, calculated on the anhydrous, acid-free basis.

2 IDENTIFICATION

Change to read:

A. ▲Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K.▲ (CN 1-May-2020)

Do not dry specimens.

3 ASSAY

Phthalyl Content

Sample solution: Transfer 1 g to a conical flask, dissolve in 50 mL of a mixture of alcohol and acetone (3:2), and add phenolphthalein TS.

Analysis: Titrate the Sample solution with 0.1 N sodium hydroxide VS. Perform a blank determination, and make any necessary correction (see Titrimetry 〈541〉).

Calculate the percentage of phthalyl on the acid-free basis:

Result = {[(1.491 × A/W) − (1.795 × B)]/(100 − B)} × 100

A = volume of 0.1 N sodium hydroxide consumed, corrected for the blank (mL)

W = weight of Cellacefate taken, calculated on the anhydrous basis (g)

B = percentage of acid found in the test for Limit of Free Acid

Acceptance criteria: 30.0%–36.0% of phthalyl (C₈H₅O₃) on the anhydrous, acid-free basis

Content of Acetyl

Sample solution: Transfer 100 mg to a glass-stoppered flask, and add 25.0 mL of 0.1 N sodium hydroxide VS. Connect the flask to a reflux condenser, and reflux for 30 min. Cool, and add phenolphthalein TS.

Analysis: Titrate the Sample solution with 0.1 N hydrochloric acid VS. Perform a blank determination (see Titrimetry 〈541〉).

Calculate the free and combined acids as acetyl:

Result = 0.4305 × (A/W)

A = volume of 0.1 N sodium hydroxide consumed, corrected for the blank (mL)

W = weight of Cellacefate taken, calculated on the anhydrous basis (g)

Calculate the percentage of acetyl on the acid-free basis:

Result = 100 × [P − (0.5182 × B)]/(100 − B) − (0.5772 × C)

P = free and combined acids, as acetyl

B = percentage of acid found in the test for Limit of Free Acid

C = percentage of phthalyl found in the test for Phthalyl Content

Acceptance criteria: 21.5%–26.0% of acetyl (C₂H₃O) on the anhydrous, acid-free basis

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

Limit of Free Acid

Sample solution: Transfer 3.0 g to a glass-stoppered flask, add 100 mL of dilute methanol (1 in 2), insert the stopper in the flask, and shake for 2 h. Filter, and wash the flask and the filter with two 10-mL portions of the methanol solution, adding the washings to the filtrate.

Analysis: Titrate the combined filtrate and washings from the Sample solution with 0.1 N sodium hydroxide VS to a phenolphthalein endpoint. Perform a blank determination on 120 mL of the dilute methanol (1 in 2) (see Titrimetry 〈541〉).

Calculate the percentage of free acid, B:

Result = 0.8306 × A/W

A = volume of 0.1 N sodium hydroxide consumed, corrected for the blank (mL)

W = weight of Cellacefate taken, calculated on the anhydrous basis (g)

Acceptance criteria: NMT 3.0%, calculated as phthalic acid

5 SPECIFIC TESTS

Water Determination, Method I 〈921〉

Sample: 0.5 g

Analysis: Dissolve the Sample in a mixture of dehydrated alcohol and methylene chloride (3:2) instead of methanol as the solvent.

Acceptance criteria: NMT 5.0%

Viscosity—Capillary Methods 〈911〉

Sample: 15 g, calculated on the anhydrous basis

Analysis: Dissolve the Sample in 85 g of a mixture of 249 parts of anhydrous acetone and 1 part of water, by weight.

Acceptance criteria: The apparent viscosity (see Viscosity—Capillary Methods 〈911〉, Method I) is between 45 and 90 centipoises, determined at 25 ± 0.2°.

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

USP Reference Standards 〈11〉

USP Cellacefate RS